1. Field of the Disclosure
The disclosed disclosure is related to downhole well investigation methods and, in particular, to measuring a resistivity property of an earth formation from a borehole containing non-conductive mud.
2. Description of the Related Art
A big challenge in oil-based mud imaging tools using electrodes is to reduce or correct the standoff effects. This is due to the fact that changes in tool standoff from the borehole wall produce variations in the current in the electrodes that mask any current variation in the formation being measured. When the standoff is large, current flow between the electrodes also become important. Capacitive coupling has been used for conveying currents into the formation, but at the high frequencies needed for capacitive coupling, the capacitance between the electrodes becomes a serious problem.
The present disclosure addresses this problem using a line source for conveying current into the formation.